// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "cc/raster/single_thread_task_graph_runner.h"

#include <stdint.h>

#include <string>

#include "base/threading/simple_thread.h"
#include "base/threading/thread_restrictions.h"
#include "base/trace_event/trace_event.h"

namespace cc {

SingleThreadTaskGraphRunner::SingleThreadTaskGraphRunner()
    : lock_()
    , has_ready_to_run_tasks_cv_(&lock_)
    , has_namespaces_with_finished_running_tasks_cv_(&lock_)
    , shutdown_(false)
{
}

SingleThreadTaskGraphRunner::~SingleThreadTaskGraphRunner() { }

void SingleThreadTaskGraphRunner::Start(
    const std::string& thread_name,
    const base::SimpleThread::Options& thread_options)
{
    thread_.reset(
        new base::DelegateSimpleThread(this, thread_name, thread_options));
    thread_->Start();
}

void SingleThreadTaskGraphRunner::Shutdown()
{
    {
        base::AutoLock lock(lock_);

        DCHECK(!work_queue_.HasReadyToRunTasks());
        DCHECK(!work_queue_.HasAnyNamespaces());

        DCHECK(!shutdown_);
        shutdown_ = true;

        // Wake up the worker so it knows it should exit.
        has_ready_to_run_tasks_cv_.Signal();
    }
    thread_->Join();
}

NamespaceToken SingleThreadTaskGraphRunner::GenerateNamespaceToken()
{
    base::AutoLock lock(lock_);
    return work_queue_.GenerateNamespaceToken();
}

void SingleThreadTaskGraphRunner::ScheduleTasks(NamespaceToken token,
    TaskGraph* graph)
{
    TRACE_EVENT2("cc", "SingleThreadTaskGraphRunner::ScheduleTasks", "num_nodes",
        graph->nodes.size(), "num_edges", graph->edges.size());

    DCHECK(token.IsValid());
    DCHECK(!TaskGraphWorkQueue::DependencyMismatch(graph));

    {
        base::AutoLock lock(lock_);

        DCHECK(!shutdown_);

        work_queue_.ScheduleTasks(token, graph);

        // If there is more work available, wake up the worker thread.
        if (work_queue_.HasReadyToRunTasks())
            has_ready_to_run_tasks_cv_.Signal();
    }
}

void SingleThreadTaskGraphRunner::WaitForTasksToFinishRunning(
    NamespaceToken token)
{
    TRACE_EVENT0("cc",
        "SingleThreadTaskGraphRunner::WaitForTasksToFinishRunning");

    DCHECK(token.IsValid());

    {
        base::AutoLock lock(lock_);
        base::ThreadRestrictions::ScopedAllowWait allow_wait;

        auto* task_namespace = work_queue_.GetNamespaceForToken(token);

        if (!task_namespace)
            return;

        while (!work_queue_.HasFinishedRunningTasksInNamespace(task_namespace))
            has_namespaces_with_finished_running_tasks_cv_.Wait();

        // There may be other namespaces that have finished running tasks, so wake
        // up another origin thread.
        has_namespaces_with_finished_running_tasks_cv_.Signal();
    }
}

void SingleThreadTaskGraphRunner::CollectCompletedTasks(
    NamespaceToken token,
    Task::Vector* completed_tasks)
{
    TRACE_EVENT0("cc", "SingleThreadTaskGraphRunner::CollectCompletedTasks");

    DCHECK(token.IsValid());

    {
        base::AutoLock lock(lock_);
        work_queue_.CollectCompletedTasks(token, completed_tasks);
    }
}

void SingleThreadTaskGraphRunner::Run()
{
    base::AutoLock lock(lock_);

    while (true) {
        if (!RunTaskWithLockAcquired()) {
            // Exit when shutdown is set and no more tasks are pending.
            if (shutdown_)
                break;

            // Wait for more tasks.
            has_ready_to_run_tasks_cv_.Wait();
            continue;
        }
    }
}

bool SingleThreadTaskGraphRunner::RunTaskWithLockAcquired()
{
    TRACE_EVENT0("toplevel",
        "SingleThreadTaskGraphRunner::RunTaskWithLockAcquired");

    lock_.AssertAcquired();

    // Find the first category with any tasks to run. This task graph runner
    // treats categories as an additional priority.
    const auto& ready_to_run_namespaces = work_queue_.ready_to_run_namespaces();
    auto found = std::find_if(
        ready_to_run_namespaces.cbegin(), ready_to_run_namespaces.cend(),
        [](const std::pair<const uint16_t,
            TaskGraphWorkQueue::TaskNamespace::Vector>& pair) {
            return !pair.second.empty();
        });

    if (found == ready_to_run_namespaces.cend()) {
        return false;
    }

    const uint16_t category = found->first;
    auto prioritized_task = work_queue_.GetNextTaskToRun(category);

    {
        base::AutoUnlock unlock(lock_);
        prioritized_task.task->RunOnWorkerThread();
    }

    auto* task_namespace = prioritized_task.task_namespace;
    work_queue_.CompleteTask(std::move(prioritized_task));

    // If namespace has finished running all tasks, wake up origin thread.
    if (work_queue_.HasFinishedRunningTasksInNamespace(task_namespace))
        has_namespaces_with_finished_running_tasks_cv_.Signal();

    return true;
}

} // namespace cc
